1. Field of the Invention
The present invention relates to a process for the production of a yarn consisting of a squared-analogous cross-section polyamide filament for uncoated airbag fabrics, to uncoated fabrics for airbags prepared by the said process, and to uses of uncoated fabrics with low air permeability prepared by the said process for the manufacture of airbags.
2. Description of Related Arts
Recently, the needs of airbags secured in vehicles is greatly increased as the recognition of the users on safety is gradually increasing, thereby protecting the drivers and passengers and reducing the occurrence of their injury.
Fabrics used for the manufacture of airbags are generally required to have low air permeability in order to achieve inflation upon being impacted and to have high strength in order to avoid rendering the airbags cracked. Further, the property of flexibility is also required in order to avoid scraping the face of passenger upon inflating.
Conventionally, in the manufacture of fabrics for airbags, it is usually necessary to apply a rubber onto the surface of fabrics in order to prepare fabrics with low air permeability. However, such a processing method presents many problems. Specifically, after the processing treatment of the fabrics, it results in many disadvantages include, for example, increasing the weight of base cloth of fabrics, lowering the flexibility, increasing the manufacture cost and difficulty of recycling, etc. Hence, there should be an active development on uncoated fabrics with low air permeability used in the manufacture of airbags.
It was known that the prior arts of, such as, Japanese Published Application Number Hei 6-41844, U.S. Pat. No. 5,073,418, Japanese Published Application Number Hei 7-252740, etc. have disclosed uncoated base fabrics.
Japanese Published Application Number Hei 6-41844 discloses a base cloth for airbags of vehicles, which is produced by the steps of: treating fabrics using chemical contraction, swelling the treated yarns, and thus preparing a base cloth with low air permeability. However, this process for the production of the base cloth results in increasing the production cost due to the proceeding of chemical treatment as well as lowering the strength of a gray yarn (i.e. a base cloth) due to the presence of chemical reagents.
U.S. Pat. No. 5,073,418 discloses fabrics with low air permeability, airbags prepared the same and the preparation thereof, which are characterized in that a cloth is woven by using (for example) less than or equal to 600 denier of a gray yarn and then processed using calendar to lower the air permeability of fabrics. However, the process disclosed in this US patent presents problems including lowering the tear strength of cloth, etc.
Further, Japanese Published Application Number Hei 7-252740 discloses a base cloth for airbags, which is prepared by using a yarn with flat-like cross-section, where the yarn as a raw material exhibits a degree of flatness of more than or equal to 1.5 in order to obtain a base cloth with low air permeability, good foldability and retractable properties and can be used as a base cloth for the manufacture of uncoated airbags. However, in this process, as the thus-prepared base cloth exhibits air permeability of more than or equal to 0.3 cc/cm2/sec at a pressure of 124 Pa, it cannot satisfy with the recent requirement of airbags that need lower air permeability.
In view of the known technologies as mentioned above, in order to solve the disadvantages and problems present in the said, the inventors of the present invention thus develop a process for the production of yarns for uncoated airbag fabrics. The thus-prepared yarns by the process of the present invention can be used in fabrics for the manufacture of airbags without additional rubber-coating process thereonto and can satisfy with the requirement of low air permeability for fabrics of airbags.